| Arsinoitherium Temporal range: 36–30 Ma Late Eocene - Early Oligocene |
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| Arsinoitherium zitteli | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Superorder: | Afrotheria |
| Order: | †Embrithopoda |
| Family: | †Arsinoitheriidae |
| Genus: | †Arsinoitherium |
| Type species | |
| Arsinoitherium zitteli Beadnell, 1902 |
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| Species | |
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Arsinoitherium is an extinct genus of paenungulate mammal related to elephants, sirenians, hyraxes and the extinct desmostylians, as well as to other extinct embrithopods. These species were rhinoceros-like herbivores that lived during the late Eocene and the early Oligocene of northern Africa from 36 to 30 million years ago, in areas of tropical rainforest and at the margin of mangrove swamps; a newly discovered species, Arsinoitherium giganteum, lived in Ethiopia ~27 million years ago.
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When alive, it would have superficially resembled a rhinoceros, and have been about 1.8 metres (5.9 ft) tall at the shoulders, and 3 metres (9.8 ft) long. The most noticeable feature of Arsinoitherium was a pair of enormous knife-like horns with cores of solid bone that projected from above the nose,[1] and a second pair of tiny, knob-like horns on top of the head, immediately behind the larger horns. The skeleton is robust but shows that it was descended from a cursorial ancestor, and that the beast may have been able to run if it had to,[1] like a modern elephant or rhinoceros. Its limb bones also suggest that the columnar legs of the living animal were elephant-like (especially since they ended in five-toed feet), rather than rhinoceros-like. Arsinoitherium had a full complement of 44 teeth, which is the primitive state of placental mammalian dentition, suggesting that it was a selective browser. The large size and hefty build of Arsinoitherium would have rendered it largely immune to predation. However, creodonts may have preyed on the young or infirm.
The name derives from Arsinoë, a Ptolemaic Egyptian queen whose palace was near the site of discovery. While this was the only site where complete skeletons of Arsinoitherium fossils were recovered, remnants of earlier relatives have been found in south-eastern Europe and Mongolia, in the form of jaw fragments. These earlier arsinoitheres have yet to be formally described. The best known (and first described) species is A. zitteli. A second species, A. giganteum, was discovered in the Ethiopian highlands of Chilga in 2003. The fossil teeth, far larger than those of A. zitteli, date back to around 28-27 million years ago[2] The Mongolian material has been named Radinskya yupingae, while the European material has been given the nomen dubium of Crivadiatherium iliescui, and the Turkish material has been named Palaeoamasia kansui (also nomen dubium).
In the book, The Macmillan Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals, the authors erroneously claim that the larger pair of horns of Arsinoitherium were hollow and cone-like,[3] a claim which was repeated in the later edition, The Simon & Schuster Encyclopedia of Dinosaurs & Prehistoric Creatures. A Visual Who's Who of Prehistoric Life[4] would be used by Tim Haines and Paul Chambers bolster their claim in their book, The Complete Guide to Prehistoric Life, that Arsinoitherium used its hollow horns as a sound resonator,[5] much in the same manner the crests of lambeosaurine dinosaurs, such as Parasaurolophus, are believed to have been used.